The invention relates to a winder for winding a traveling web, wherein two king rolls form a winding bed for accommodating a paper roll. A revolving support belt loops around the paper roll, over part of its circumference.
In winding webs, the winding hardness is a significant factor for further processing. Particularly with paper webs it is very important for the winding hardness to have a specific progression across the entire paper roll diameter.
In general, the winding hardness should drop from a certain initial value to a final value. The drop should be maximally uniform from the first to the last layer. The drop should have a certain gradient, that is, should not be too heavy and not too light. The progression of the winding hardness should not at any rate include jumps, for instance a sudden drop. This can be accomplished only by specific measures. When letting things go, the line pressure between the paper roll and the king roll(s) becomes ever greater, and with it also the winding hardness.
A winder of this general type is known from DE 38 39 244. This winder features three king rolls. The first is stationary while the following two are movable and looped by a support belt. The support belt and the positional change of the second and third king roll serves to control the winding hardness across the entire paper roll diameter. The objective for the support belt is to provide a maximally large support surface in order to reduce the surface load. This winder is extremely expensive. In addition, it has a particularly grave disadvantage: once the paper roll has grown such that it is carried primarily by the support belt, strong vibrations may occur in the support belt, as a result of which the paper roll starts "dancing" and can be catapulted out of the winding bed.
Other measures for influencing the winding hardness are distributing the load of the paper roll among the individual king rolls. For that purpose, king rolls of equal diameter have been arranged already in different horizontal planes, or king rolls with different diameters were used. It is also known that winding on a king roll with a smaller diameter will produce a harder paper roll than winding on a king roll with a larger diameter.
Known from DE-DM 7 310 606 is a winder featuring two king rolls of equal size. One of them can during the winding operation be lowered from an upper position above the horizontal plane of the axis of the other king roll at the beginning of the winding operation. The objective of this lowering is to obtain a firmly wound core from the outset.
U.S. Pat. No. 2,461,387 describes a winder that includes two powered king rolls of different diameters. The one with the smaller diameter has a coating with a greater coefficient of friction and is powered at a higher speed than the other king roll, thereby exerting a tension on the outer layer of the web.
DE-OS 27 57 247 concerns a winder with king rolls of the same diameter. The winding hardness is controlled by variation of the mutual spacing of the king rolls.
DE-PS 678 585 describes a winder with two king rolls of which the first has a hard shell and the second a soft shell. The axes of the two rolls are situated in one and the same horizontal plane.
DE-A-44 02 624 shows and describes a winder where the space bounded by the king rolls and the paper roll is fashioned as a pressure-tight chamber with a port for compressed air. Air volume and air pressure can be controlled in keeping with the growing weight of the paper roll. However, this involves appreciable problems in sealing the pressure chamber.
The problem underlying the invention is therefore to configure a winder of this general type in such a way that a controlled winding hardness is achievable across the winding diameter, that the diameter of the individual paper roll can be chosen still greater than heretofore, without inviting the feared busting of the outer turns of the paper roll, and that--most of all--air inclusions between the paper roll layers will be avoided.